1. Field of the Invention
The invention re1ates to a remote actuating mechanism having a driver, a transmission unit and a remote actuating lever.
2. Description of the Prior Art
Remote actuating mechanisms are known for a variety of purposes. European Patent Application-No. A2-0 131 711 describes a remote actuating mechanism for a lever of a three-point implement hitch of an agricultural tractor which is used for shifting the lever, arranged in the driver's cab of the tractor, from outside the cab, so that draft links belonging to the three-point implement hitch can be raised or lowered without an operator having to climb onto the tractor. It is often the case in agricultural applications that, depending upon the design of the control and adjustment equipment of the three-point implement hitch, the lever is permitted to be moved only within a certain range. This is dependent, inter alia, on whether the adjusting device can carry out position adjustment and tractional resistance adjustment or not. The controls and adjustment equipment are designed such that selection of position adjustment causes shifting of the lever to produce a proportiona1 movement of the draft links over their entire range. Selection of tractional resistance adjustment causes shifting of the lever to first produce no movement of the draft links while the lever passes through a dead range located at the beginning of its travel and an uncontrolled movement of the draft links in an adjustment range that follows the dead range so long as there is no tensile stress at the draft links. Uncontrolled movement of the drafts links is undesirable when operating the remote lever, therefore it is advantageous to design the lever such that it cannot be brought into the adjustment range when tractional resistance adjustment has been chosen as the kind of adjustment.
The remote actuating mechanism of European Patent App1ication-No. A2-0 131 711, uses a driver in the form of a pinion and a transmission unit in the form of a rack with a Bowden cable attached thereto. The pinion is provided with teeth only over part of its circumference, is rotatabIy mounted in a housing, and can be connected to a remote actuating lever by means of a simple pivot connection in opposition to the action of a spring element. The rack takes the form and function of a slide which is longitudinally movable in the housing or through engagement with the pinion, in which case the rack supplies input to the cable. Two stops which limit the range of swing of the remote actuating lever to a predetermined range which corresponds to the dead range are provided on the housing. In another embodiment of this remote actuating mechanism, a pawl engages in the pinion as soon as the rack is located at the end of the dead range. Outside the dead range the pawl is held by a special recess into engagement with the rack so that the pinion can be turned neither forward nor backward.
This remote actuating mechanism suffers from drawbacks presented by pivotal engagement of the pinion with the remote actuation mechanism. First, supplying and maintaining sideways force to engage the pinion complicates operation of the lever. Furthermore, the pivot connection can be bypassed by placing the remote actuating lever laterally against the pivot so that the rotary movement of the pinion leads to swinging movement of the remote actuating lever and the rack is moved beyond the predetermined range. Likewise, the remote actuating lever can also be pushed into frictional contact against the pinion and hence the rack can be shifted beyond the predetermined range.
It is true that the last two drawbacks are avoided in the embodiment with the pawl. The cost of adding the pawl is unjustifiably high, however. Furthermore, after a long period of use wear, at the pinion, the rack, and the tip of the pawl will cause this locking device to function improperly and will lead to blocking of the remote actuating mechanism.